Unable to create a new session key. It is likely that the cache is unavailable.
/etc/memcached.conf
の#-l 127.0.0.1
をコメントアウトしてその下に-l 0.0.0.0
を追記
/etc/memcached.conf
# Specify which IP address to listen on. The default is to listen on all IP addresses
# This parameter is one of the only security measures that memcached has, so make sure
# it's listening on a firewalled interface.
# -l 127.0.0.1
-l 0.0.0.0